I have a cold idle problem with my M606 ( a problem with M606!) whereby the idle needs to controlled by throttle until warm othewise it threatens to stall.

I have eliminated OVP, glow plugs and air in the fuel lines as potential causes thanks to diagnostic suggetions picked up from searching this forum.

What else controls the cold idle speed and how can i diagnose ?

thanks in advance
Keith

I would triple check the fuel lines.

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'97 E300
'99 E300

in past had air in fuel lines before but this feels different. Air in the lines made it difficult to start as well as idle. In this case starting is easy, first turn every time. Its just the idling thats rough when cold.

Keith